Radiolysis of paracetamol in dilute aqueous solution

Using radiolytic experiments hydroxyl radical (main reactant in advanced oxidation processes) was shown to effectively destroy paracetamol molecules. The basic reaction is attachment to the ring. The hydroxy-cyclohexadienyl radical produced in the further reactions may transform to hydroxylated paracetamol derivatives or to quinone type molecules and acetamide. The initial efficiency of aromatic ring destruction in the absence of dissolved O₂ is c.a. 10%. The efficiency is 2–3 times higher in the presence of O₂ due to its reaction with intermediate hydroxy-cyclohexadienyl radical and the subsequent ring destruction reactions through peroxi radical. Upon irradiation the toxicity of solutions at low doses increases with the dose and then at higher doses it decreases. This is due to formation of compounds with higher toxicity than paracetamol (e.g. acetamide, hidroquinone). These products, however, are highly sensitive to irradiation and degrade easily.     

A study of pervaporation of aqueous benzyl alcohol solution by polydimethylsiloxane membrane

Pervaporation of dilute benzyl alcohol solutions was attempted using polydimethylsiloxane (PDMS) membranes. The effects of temperature, downstream pressure and the solution concentration as operating variables on the membrane performance were investigated. It was possible to concentrate benzyl alcohol ten fold in the permeate at the downstream pressure of 66.7 Pa (0.5 mmHg) activity coefficient of benzyl alcohol in the aqueous solution. The permeate concentration, however, decreased and became even less than the feed concentration at high downstream pressures. An increase in the operating temperature increased the vapor pressure of benzyl alcohol and, consequently, increased the permeate concentration. As a result, more than seventy fold increase of benzyl alcohol in the permeate was possible at an operating temperature of 40°C.     

Radiolysis of phenol in aqueous solution at elevated temperatures

γ-Radiolysis and pulse radiolysis of phenol in aqueous solution up to supercritical condition have been carried out. G-values of phenol consumption and product formation have been determined. While dihydroxybenzenes were major products at room temperature, multi-ring compounds and benzene were formed above 300 °C. This indicates reaction mechanism was changed above 300 °C, where phenoxyl radical plays a predominant role. This is supported by the observation of phenoxyl radical in pulse radiolysis. In supercritical water, the G-values increased with decrease of density.     

Radiolysis of alkyl benzene sulfonat (ABS) in aqueous solution

Degradation of alkyl benzene sulfonate (ABS) in aerated aqueous solution irradiated with gamma radiation with doses up to 1.8 kGy were studied. The degree of degradation, pH change, the effect of pH on the degradation, COD values and the degradation products were determined. The degradation of ABS increases with the increase of doses and decreases with the increase of ABS concentration. The degradation was somewhat more efficient in slightly acidic and neutral solutions than at basic pH oxalic acid was detected by HPLC as degradation product.     

N2O饱和黄芩苷水溶液的辐解机理

本工作研究了γ辐解N2O饱和黄芩苷水溶液的辐解机理, 发现四种主要辐解产物(P1, P2, P3, P4)。紫外、质谱和核磁共振谱确定了它们的化学结构。其中P1, P2为OH自由基与C环作用失去B环形成的, 而P3, P4为OH自由基加成到B环并发生歧化反应的的结果。求得OH自由基与黄芩苷的苷元发生加成反应的速率常数为: 2.6×10^9mol^-^1.dm^3.s^-^1。     

Relative rates of nucleophilic reactions of benzyl carbocation formed in photolysis of benzyl chloride and benzyl acetate in aqueous solution

Benzyl chloride and benzyl acetate were photolyzed in 30% methanol–water mixtures (V/V) at 0°C. The photolysis produces benzyl carbocations that react with nucleophiles. The reaction products were analyzed by gas chromatography or liquid chromatography. From the amounts of products the relative values of rate constants of reactions of benzyl carbocation with nucleophiles N and water k(N)/k(H₂O) were calculated. Benzyl carbocation reacts with I^?, Br^?, Cl^?, and Ac^? ions with approximately diffusion-controlled rate. A value of 2.4 × 10⁷ dm³ mol^?1 s^?1 for the rate constant k(H₂O) and a lifetime of 0.7 ns were estimated for benzyl carbocation in the aqueous solution.     

Photosolvolysis of 2-aminobenzl alcohol in aqueous solution

The photosolvolytic behavior of 2-aminobenzyl alcohol (4) was studied in aqueous solution over a range of pH and in moderately concentrated aqueous H₂SO₄ solution. Although reactive at all pH values studied, clean solvolytic reaction was observed only when pHK_a (for ground state dissociation of aryl ammonium ion). A mechanism of reaction in acidic medium is proposed in which the protonated substrate (ArNH₃⁺) is excited to S₁ and then undergoes adiabatic deprotonation to give the electronically excited free base. Subsequent dehydroxylation, which can be assisted by a proton, gives o-quinone methide imine (o-QMI, 5) as the reactive intermediate. Nucleophilic attack by added ROH gives the photosolvolytic product. If pH>pK_a, a significant proportion of 5 reacts with free amine 4, which is sufficiently nucleophilic to compete with H₂O or ROH, eventually giving rise to oligomeric products.     

Radiolysis of pyridoxine (vitamin B6) in aqueous solution under different conditions

Aqueous solutions of pyridoxine (1 mM) without or with additive of K₃[Fe(CN)₆] (2.5 mM) were gamma-irradiated at different doses and dose rate of 2.16 kGy/h in the absence of air, in the presence of air or by their saturation with N₂O. The radiolytic products were analyzed with HPLC, mass spectrometry and UV spectroscopy. 2,4,5-Trihydroxymethyl-3-pyridinol, pyridoxal, isopyridoxal and 6-hydroxypyridoxine were formed by radiolysis in the absence of K₃[Fe(CN)₆], and their concentrations were much higher in samples saturated with N₂O. Pyridoxi-3,6-quinone was found by radiolysis under all the above-mentioned conditions but only in the presence of K₃[Fe(CN)₆]. Besides, the pyridoxal formation increased in the presence of this oxidizing agent. G values of pyridoxal formation and pyridoxine degradation were quantified. Some details of the radiolytic product formation were discussed.     

Radiolysis of aqueous cesium iodide

In hypothetical accident scenarios for Light Water reactors, the extent of release of iodine upon irradiation needs to be assessed for the purpose of evaluation of the applicable source term. In this context, an understanding of the behaviour of aqueous cesium iodide solutions subjected to high gamma-ray fluxes acquires significant importance. In the present work, gamma radiolysis of a cesium iodide solution (10^–2M I^–) with and without boron additive is investigated by irradiating with⁶⁰Co source at ambient temperature. Upon irradiation of the CsI solution, iodine is liberated, and the concentration of iodide in the KOH trap present in the radiolysis vessel increases with dose. The radiolytic products I ₃ ^– , IO ₃ ^– and H₂O₂ formed in the irradiated solution are also estimated and G values obtained are reported. G(I ₃ ^– ) and G(IO ₃ ^– ) are of the order of 10^–3 and 10^–4, respectively. G(H₂O₂) decreases with increase in dose. Addition of boron up to 200 ppm, does not appear to alter significantly the release fraction of iodine.     

Radiolysis and variation of anti-microbial activity of gamma-irradiated acrinol aqueous solution on radiosterilization

The investigations about the radiolysis materials and their quantities, and, anti-microbial activities of gamma-irradiated (in the ranges of 0.516-2.064 kC/kg (2-8 MR] acrinol on liquid dosage form have been carried out to study the application of radiosterilization. About nine components were found as radiolysis materials. Most of them were also found in the UV-irradiated of Fenton's reagent-treated acrinol solution. Increase of anti-microbial activity was observed with gamma-irradiated acrinol solutions, but this phenomenon was not long-lasting. The micro-organism such as Pseudomonas aeruginosa or Staphylococcus aureus that infect at the lips of wound are highly sensitive to the gamma-irradiation. They are almost sterilized by the irradiation of 10 kGy (1.0 Mrad). At a low acrinol concentration, the decomposition rate of acrinol by the irradiation was relatively high. When 1.0% of acrinol solution was irradiated at a dose of 10 kGy (1.0 Mrad), the decomposition of the drug was less than 2% and the variation of anti-microbial activity was negligible.     

Radiolysis of 1-naphthol in aqueous solutions

The effects of absorbed doses, initial pH and 1-naphthol concentration onto its radiolysis in aqueous sulphuric and hydrochloric acids by gamma rays from ⁶⁰Co were investigated. Under the experimental conditions, 1-naphthol degradation yields increased with increasing the absorbed doses (0.3–3.0 kGy) and with decreasing the initial 1-naphthol concentration (20–1 ppm). It was found out that the hydrated electrons did not play any significant roles in 1-naphthol radiolysis, as the degradation yields were higher at pH₀ ~ 0.46 compared to those at pH₀ ~ 2.0–5.0. The corresponding radiolytic yields G(−1-naphthol) were (6.13 ± 1.00)) × 10⁻² and (5.11 ± 0.22) × 10⁻² μmol/J in sulphuric acids, (15.61 ± 3.85) × 10⁻² and (4.76 ± 0.48) × 10⁻² μmol/J in hydrochloric acids. 1-Naphthol degradation rates could be described by the kinetic equations of pseudo-first-order reactions. An empirical relation between the observed reaction constants k _D and the initial 1-naphthol concentrations was established, enabling to predict the absorbed doses required for a given treatment efficiency. Three products of 1-naphthol degradation were revealed using an HPLC/UV procedure.     

Radiolysis of aqueous solutions of thiamine

The results of the radiolysis of aqueous solutions of thiamine (vitamin B₁) are presented. The yields for decomposition of thiamine and the product of radiolytic products were determined. The G values decrease as the dose increases. Some radiolytic products were identified. Decomposition of thiamine was slightly dependent on the presence of oxygen and on the pH of the solution. At pH 4.4 with a concentration of 2.5 × 10⁻⁴ mol L⁻¹ of thiamine in an oxygen free aqueous solution, the G⁰ value for decomposition is 5.0.     

Radiolysis of aqueous solutions of poly(vinyl alcohol) at 77 K

Paramagnetic products of low-temperature X-ray radiolysis of aqueous poly(vinyl alcohol) solutions (2.5 and 5% by weight) were studied by ESR spectroscopy. Experimental spectra were ascribed to a superposition of signals from hydroxyl radicals and –CH₂?^?C(OH)–CH₂? macroradicals (C_α-macroradicals), respectively. No ESR signals corresponding to trapped electrons were observed that was attributed to the peculiarities of microheterogenous structure of the frozen aqueous polymer solutions. Annealing at 115 K resulted in partial conversion of OH radicals to C_α-macroradicals. It was suggested that main part of hydroxyl radicals was stabilized in phase of polycrystalline ice while macroradicals were formed in “mixed” water–polymer phase. The radiation–chemical yields of paramagnetic species stabilized in the systems under study were determined.     

Aerobic oxidation of alcohol in aqueous solution catalyzed by gold

The heterogeneous oxidation catalyzed by supported gold nanoparticles has been relatively well studied. In comparison, the oxidation of alcohols catalyzed by ligand-supported gold complexes was rarely reported. Herein a general method is demonstrated to oxidize secondary and primary benzyl and allylic alcohols to carbonyl compounds via Au(I) catalyzed reaction in air and water. Primary mechanistic studies indicated that the catalytic pathway is different from those catalyzed by solid-supported gold nanoparticles.     

Radiolysis of aqueous-ethanolic solution of tryptophan

The effect of ethanol on radiation stability of tryptophan during -irradiation of its aqueous solutions was investigated. In comparison with radiation losses of tryptophan irradiated in pure water, the losses in aqueous-ethanolic solutions are considerably higher and they increase with increasing ethanol concentration. Basic radiation products of tryptophan formed on irradiation of its aqueous-ethanolic solutions in consequence of the reaction of tryptophan with acetaldehyde as the main product of radiolysis of ethanol were followed by paper electrophoresis.     

Radiolysis of rutin in aerated ethanolic solution

Radiolysis of rutin was performed in aerated ethanolic solution. Two major radiolytic products (RP1, RP2) were isolated by HPLC, and their possible structures were deduced from their UV, IR and MS spectra, and elementary analysis as well. The G-values of RP1 and RP2 increase with increasing rutin concentration, and in all cases both of them equal the G-value of rutin consumption. The addition of rutin leads to the decrease of G(H₂O₂) but has little effect on G(CH₃CHO). Therefore the formation of RP1 and RP2 was proposed to be from further addition of HO%s₂ to the phenolic radical (generated from H-abstraction by HO%s₂) followed by fragmentation.     

Radiolysis study of genistein in methanolic solution

The aim of the present work was to identify products obtained from genistein by ionizing radiation and to enhance the antioxidant properties of genistein through radiation-induced transformation. Genistein dissolved in methanol was irradiated γ-rays at a dose of 100 kGy. NMR and (HR) EI-MS spectroscopy were used to identify radiolysis products (GM1 and GM2). We proposed that CH₂OH may be implicated in the formation GM1 and GM2 during radiolysis of genistein in methanol. The genistein in methanol solution showed higher DPPH radical scavenging activity after γ-irradiation. Then, the antioxidant activities of radiolysis products were evaluated and compared to those of genistein.